London, England (CNN) -- Britain's prime minister on Tuesday defended the mission in Afghanistan as "vital" to protecting his country from terrorists, following the death of the 100th British serviceman in Afghanistan this year.
The soldier, from the 1st Battalion The Royal Anglian Regiment, was killed Monday by small arms fire in the Nad-e Ali area of Afghanistan's southern Helmand province, Britain's Ministry of Defence said.
His name was not released, but the soldier's next of kin were informed, the ministry said.
The soldier was the 100th member of the British armed forces to die in Afghanistan this year, the ministry said. Britain has lost more than 200 service personnel in the country since the start of fighting in 2001.
British Prime Minister Gordon Brown emphasized the "real impact" of the Afghan mission as he offered his condolences to the soldier's family.
"Our military presence in Afghanistan means that al Qaeda cannot use the country as a base from which to plot terrorist attacks against Britain," Brown said in a statement Monday.
"And the work of our armed forces in the next stage of the campaign, the training and partnering of the Afghan security forces to do this job for themselves, along with the political and civilian development of the country, will be vital in ensuring the British people are safer for generations to come."
British Defence Secretary Bob Ainsworth also defended the importance of the mission to security at home.
"I believe we must keep at the forefront of our minds why our people are in Afghanistan," Ainsworth said in a statement. "Our presence in Afghanistan is vital in preventing it from once again becoming a haven for terrorists who would seek to threaten the UK."
Ainsworth said "taking the fight to the insurgents" -- along with providing security and training Afghan security forces -- will help Afghanistan become stable and independent.
The death came a week after Brown announced that the UK would send an extra 500 troops to Afghanistan in early December, bringing the British contingent there to more than 9,500.
Brown regularly links British security to events in Afghanistan and Pakistan, saying attacks on London and other British targets have been planned in South Asia.
He announced in October the decision in principle to boost force levels but said certain conditions -- including proper equipment for the British troops and more troop commitments from other countries -- had to be met first.
The UK has the largest contingent in Afghanistan after the United States. The figure of 9,500 does not include special forces, said Brown, who declined to say exactly how many of those were there, but indicated it is more than 500.